The nuclear lamins are type V intermediate filament proteins that form meshworks at the inner aspect of the nuclear envelope and are also present throughout the nuclear interior. Through these meshwork structures, lamins regulate the shape, size, and mechanical properties of the nucleus. During the last 25 years, the Goldman laboratory has studied the organization and dynamic properties of the lamins in the nucleus. These studies have characterized the role of lamin phosphorylation in nuclear lamina assembly and disassembly during mitosis. Furthermore, our studies have demonstrated a role for the lamins in chromatin modification and epigenetics, transcription, and DNA replication. Recently, the discovery of numerous mutations in the gene encoding A-type lamins causing the collection of diseases known as laminopathies has provided new insights into the roles of lamins in cellular regulation and differentiation.